CO2 sorbent for inhalation drug therapy system

ABSTRACT

A carbon dioxide (CO 2 ) sorbent system for removing CO 2  from a recirculating inhalation therapy system includes several sorbent layers within a housing defining an inlet and an outlet. Airflow passages sandwiched between CO 2  sorbent layers allow airflow from the inhalation therapy system through the CO 2  sorbent assembly. The recirculating inhalation therapy system controls the amount of CO 2  within the system without removing aerosol medication contained within the breathable air stream.

BACKGROUND OF THE INVENTION

[0001] This invention relates to a system for removing carbon dioxide(CO₂) emissions from an inhalation therapy system, and specifically to aCO₂ sorbent assembly for extracting metabolically produced CO₂ fromexhaled air.

[0002] Many diseases and medical conditions are currently being treatedby inhalation therapy in which an aerosol medication is inhaled by apatient. Such treatments require inhalation of a proportionally largeamount of aerosol medication relative to a low amount of medication thatis actually absorbed into the patient's lungs. A relatively large amountof medication is wasted simply by being exhaled during a normalbreathing cycle.

[0003] Currently systems for controlling and eliminating CO₂ from abreathable air supply are utilized in diving applications, submarines,space vehicles and space suits. These systems utilize a CO₂ sorbent bedcomposed of a solid or liquid sorbent disposed within a container. Astream of air containing CO₂ is flowed through the container and thesorbent. The CO₂ reacts with the sorbent, trapping CO₂ within thecontainer. The remainder of the breathable air recirculates into thecontrolled environment. Once the container has become saturated with CO₂such that further absorption of CO₂ is inefficient, the breathable airstream is switched to a second container. The saturated container iseither disposed or regenerated. Such systems have proven effective andefficient for controlling CO₂ content within enclosed environments;however, these sorbent systems would tend to remove aerosolizedparticles within the air stream during inhalation therapy.

[0004] Accordingly, it is desirable to employ CO₂ sorbent technology inan inhalation therapy system for controlling CO₂ levels and increasingsystem efficiency by reusing exhaled aerosol medication.

SUMMARY OF THE INVENTION

[0005] A disclosed embodiment of this invention is an assembly forcontrolling the amount of carbon dioxide (CO₂) within a recirculatinginhalation therapy system with a CO₂ sorbent while allowing reuse ofmedication in aerosol form by the inhalation therapy system.

[0006] The assembly of this invention removes CO₂ from a recirculatinginhalation therapy system with a CO₂ sorbent. The CO₂ sorbent assemblyincludes several CO₂ sorbent layers disposed within a housing. Thehousing includes perforated sheets defining an inlet and an outlet.Between the CO₂ sorbent sheets is an airflow passage. The airflowpassage is unobstructed by CO₂ sorbent, allowing the free flow of airthrough the assembly. Carbon dioxide is drawn from the airflow andabsorbed in the CO₂ sorbent. Because the airflow proceeds through theCO₂ sorbent assembly uninterrupted, any aerosol medication remaining inthe exhaled air of the patient will proceed directly through andsubstantially uninhibited by CO₂ sorbent assembly for readministrationto the patient. In this way, a substantial amount of otherwise wastedmedication input into the system is administered to the patient.

[0007] Accordingly, the CO₂ sorbent assembly of this invention controlscarbon dioxide within a recirculating inhalation therapy system withouttrapping aerosol medication.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The various features and advantages of this invention will becomeapparent to those skilled in the art from the following detaileddescription of the currently preferred embodiment. The drawings thataccompany the detailed description can be briefly described as follows:

[0009]FIG. 1A is a perspective view of the embodiment of the CO₂ sorbentassembly;

[0010]FIG. 1B is a cross-sectional view of an air passage configuration;

[0011]FIG. 1C is a cross-sectional view of another embodiment of an airpassage configuration;

[0012]FIG. 2A is a perspective view of another embodiment of the CO₂sorbent assembly;

[0013]FIG. 2B is side view of the embodiment of FIG. 2A;

[0014]FIG. 3 is a schematic diagram of an inhalation therapy system; and

[0015]FIG. 4 is a schematic diagram of a device to regenerate saturatedCO₂ sorbent.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0016] Referring to FIG. 1A-C, a disclosed embodiment of this inventionis a carbon dioxide (CO₂) sorbent assembly 12 for an inhalation therapysystem 10. The CO₂ sorbent assembly 12 includes an inlet and outlethaving perforated sheets 14 to allow airflow indicated by arrow 24 topass through the assembly 12. Disposed within the assembly 12 are CO₂sorbent sheets 16. The CO₂ sorbent sheets 16 are comprised of CO₂sorbent material. The specific type of CO₂ sorbent can by of any typeknown to a worker skilled in the art.

[0017] The CO₂ sorbent layers 16 combine to define airflow passage 22through the assembly 12. Airflow through the assembly 12 is drawn intothe CO₂ sorbent by a pressure gradient created by the normal breathingcycle of a patient drawing air through the airflow passages 22. Theexhaled air flow 24 is directed into the CO₂ sorbent. The amount of CO₂absorbed by the assembly 12 depends on the flow rate of the exhaled air,the number of sorbent sheets 16 and the dimensions of the airflowpassages 22. The higher the number of sheets 16, the greater the amountof CO₂ absorbed. The larger the airflow passage 22, the less carbondioxide absorbed by the CO₂ sorbent assembly 12. A smaller airflowpassage 22 results in a shorter diffusion path for the CO₂ and a greateramount of CO₂ is absorbed by sorbent layers16. The number of sorbentsheets 16 and the specific dimensions of the airflow passage 22 areapplication specific and a worker knowledgeable in the art wouldunderstand how to vary these dimensions to produce the desired amount ofCO₂ absorption.

[0018] The CO₂ sorbent sheets are wrapped in a Teflon wrap 18. TheTeflon wrap 18 allows permeation of CO₂ without allowing the release ofCO₂ sorbent into the inhalation therapy system 10. Further, the sorbentlayers 16 are separated from the airflow passage 22 by perforated sheets34. The perforated sheets 34 provide structural support for the CO₂sorbent 16 from the air flow passage 22.

[0019] Disposed within the sorbent layers 16 are air passage fins 20.The air passage fins 20 define the airflow passage 22 through theassembly 12 (FIG. 1B). In this embodiment, the air passage fins 20include an alternating series of channels comprised of peaks 19 andvalleys 20 defining the airflow passage through the CO₂ sorbent assembly12. The air passage fins 22 are a separate part sandwiched betweensorbent layers 16. Referring to FIG. 1C, another embodiment of thisinvention is shown where the sorbent layers are formed with analternating series of channels and peaks to define the airflow flowpassage 22 without the need for the air passage fins 20.

[0020] Aerosol medication contained within the airflow 24 flows throughthe assembly 12 and is not absorbed or trapped within the CO₂ sorbentlayers 16. Airflow through the assembly 12 flows by the CO₂ sorbentlayers 16 and therefore allows aerosol medication exhaled from a patientto pass through the assembly 12.

[0021] Referring to FIG. 2, another embodiment of the CO₂ sorbentassembly is shown and generally indicated at 40. In this embodiment theCO₂ sorbent assembly 40 is cylindrical with a series of spirally woundsorbent sheets 42 alternating between layers of air passage fins 46defining an air passage through the sorbent assembly 40. The cylindricalhousing defines an inlet 50 and an outlet 48. The open space betweensorbent layers 42 defines the air passage 46 through the CO₂ sorbentassembly.

[0022] The sorbent assembly 40 includes a diameter and a length 56, 58and air passage fins 56. The diameter 56 and length 58 are sizedaccording to certain applications specific requirements such as airflowrate and desired amount of CO₂ absorption.

[0023] Referring to FIG. 3, a block diagram schematically illustratingthe inhalation therapy system 10. In such a system, the patient isenclosed within a containment chamber indicated at 70. It should beunderstood that the containment chamber may be a mask, an oxygen tent orany other structure known to a worker in the art for administering arecirculating breathable air supply.

[0024] The patient breathes in aerosol medication introduced into thesystem 10 by way of a nebulizer indicated at 72. As the patient inhalesthe medication, a certain amount of the aerosol medication remainswithin the patient and a certain amount is exhaled from the patient.Along with the exhaled excess aerosol medication, a certain amount ofCO₂ is exhaled as is normal during the breathing cycle. Air exhaled fromthe patient within the patient enclosure 70 is directed into a CO₂sorbent assembly 12,40 to remove a desired amount of CO₂. The desiredamount of CO₂ is removed from the system while minimizing the amount ofaerosol medication deposited within the sorbent assembly. Air drawn intothe CO₂ sorbent assembly 12, 40 is then output back into the patientenclosure 70. The inhalation therapy system illustrated in FIG. 3 isonly one possible configuration and illustrates operation of the CO₂sorbent assembly 12, 40.

[0025] Referring to FIG. 4, an embodiment of a regeneration system 80 isschematically shown. In the applications where the CO₂ sorbent assembly12,40 comprises a regenerable sorbent such as silver oxide or molecularsieve, a regeneration assembly 80 is used to regenerate the CO₂ sorbentfor re-use and sterilization. The regeneration system 80 includes theheating element 84. An airstream 84 is directed past the heating element84 and then to the solvent assembly 12. The heated air provides a meansof heating the sorbent to its regeneration temperature and sweeps theevolved CO₂ from the sorbent assembly 12.

[0026] The CO₂ sorbent assembly of this invention provides regulationand control of CO₂ within an inhalation therapy system withoutsubstantially absorbing exhaled aerosol medication. Control of the CO₂within the inhalation therapy system allows for the re-breathing ofexhaled aerosol medication that was not absorbed by the patient. There-breathing of the aerosol medication provides a more efficient andcost effective inhalation therapy system 10.

[0027] The foregoing description is exemplary and not just a materialspecification. The invention has been described in an illustrativemanner, and should be understood that the terminology used is intendedto be in the nature of words of description rather than limitation. Manymodifications and variations of the present invention are possible inlight of the above teachings. The preferred embodiments of thisinvention have been disclosed, however, one of ordinary skill in the artwould recognize that certain modifications are within the scope of thisinvention. It is understood that within the scope of the appendedclaims, the invention may be practiced otherwise than as specificallydescribed. For that reason the following claims should be studied todetermine the true scope and content of this invention.

What is claimed is:
 1. An inhalation therapy system comprising; acontainment chamber for administering a recirculating breathable airsupply; a device for introducing aerosol medication into saidrecirculating breathable air supply; a CO₂ sorbent assembly forcontrolling CO₂ content and defining a passage said breathable airsupply.
 2. The system of claim 1, wherein said CO₂ sorbent isencapsulated within a porous material providing containment of said CO₂sorbent.
 3. The system of claim 1, wherein said CO₂ sorbent includesseveral layers and said passage is disposed between said layers of CO₂sorbent.
 4. The system of claim 1, further including air passage finsdefining said air passage between said layers of CO₂ sorbent.
 5. Thesystem of claim 4, wherein said air passage fins are integrally formedwithin said CO₂ sorbent.
 6. The system of claim 1, wherein said CO₂sorbent is regenerable.
 7. The system of claim 1 wherein said CO₂sorbent is silver oxide.
 8. The system of claim 1, wherein said CO₂ isnon-regenerable.
 9. The system of claim 1, wherein said CO₂ sorbent issodasorb.
 10. The system of claim 1, wherein said CO₂ sorbent is lithiumhydroxide.
 11. The system of claim 1, further including a regenerationdevice including a heating element and an air flow device for flowingair through said regeneration device and heating said CO₂ sorbent toexpel CO₂.
 12. A method of removing Carbon Dioxide (CO₂) from aninhalation therapy system comprising the steps of: a.) passing a streamof exhaled air past a CO₂ sorbent; b.) absorbing a portion of CO₂ fromwithin said exhaled air; c.) passing exhaled medication through said CO₂sorbent for re-inhalation by a patient.
 13. The method of claim 12,wherein said step (a.) is further defined by passing a stream of exhaledair between layers of the CO₂ sorbent.
 14. The method of claim 12,further including the step of regenerating said CO2 sorbent by expellingabsorbed CO₂.